This invention relates to lancet devices of the kind used to produce incisions in the skin for the purpose of releasing small amounts of blood therefrom.
The prior art is replete with cutting devices used to make small incisions in the finger or some other accessible tissue of the patient. A wide variety of lancet devices has been described, some of which have been commercialized. In general, they comprise cutting components located in a housing which conceals the cutting device and the actuating motion which causes the blade to be protected out of the housing and into the patient's tissue. Usually, the blade communicates with a restrained spring means and responds to the uncoiling action of the spring means upon release of the restraint. The blade then moves in a linear or a rotational motion through the housing and into the tissue site to be cut. Oftentimes, such devices are painful or inconvenient to use.
In the prior art, there exist many different designs for providing such incisions. Modern devices are usually designed for single-use, disposable operation and utilize a spring-loaded mechanism for accelerating the blade or needle through the course of its cutting motion. In general, three main types of lancet devices are encountered in the prior art. They may be classified as "stab", "slap", and "slice" devices.
The simplest of these is the "stab" group, to which the majority of prior art devices belongs. Devices of this group, exemplified by U.S. Pat. No. 4,889,117 issued on Dec. 26, 1989 to Stevens entitled DISPOSABLE LANCET and U.S. Pat. No. 4,553,541 issued to Bums entitled AUTOMATIC RETRACTABLE LANCET ASSEMBLY, employ a sharp, pointed needle or blade which is driven directly into the patient's skin with a puncturing action. The needle or blade may then be retracted back into its housing. Devices of this type have an advantage in their simplicity, though they cannot offer a completely controllable incision, nor do they attempt to address the needs of patients more susceptible to epidermal trauma, such as the elderly or the newborn.
Lancet devices of the "slap" group are similar in many ways to the "stab" group. For example, in U.S. Pat. No. 3,760,809 to Campbell, Jr. entitled SURGICAL LANCET HAVING CASING, a sharp blade is affixed to a flexible member inside the housing. In the starting position, this flexible member is bent at one end and hooked to the release mechanism at the roof of the housing. When activated, the energy stored in the flexible member is released, slapping the blade down through a sealed membrane and into the patient's skin. The incision produced is very similar to those produced by "stab" devices. Though they operate very quickly, both "stab" and "slap" devices produce an incision of nonreproduceable depth and can cause patient discomfort. Retracting the blade requires a complicated mechanism, or is not done at all in prior art devices of these types.
The third type of prior art device is the group characterized by blades which move primarily in a direction parallel to the skin of the patient, using a slicing motion to create an incision. In U.S. Pat. No. 5,314,441 to Cusack, et. al. entitled DISPOSABLE SLICING LANCET ASSEMBLY, a blade, sharpened only on one vertical edge, is attached to a fixed pivot point in the center of the housing. A torsional spring drives the rotating motion of the blade around this fixed pivot point, causing the blade to exit the housing, perform a slicing incision in the patient's skin, and then reenter the housing for the balance of its motion. Further, the path of the blade need not be purely circular; using an elongated slot in the blade, motion in the radial direction may also be accomplished. This allows the path of the blade to be specified precisely, by implementing a guide slot embossed on an interior wall of the housing. In U.S. Pat. No. 4,643,189 to Mintz entitled APPARATUS FOR IMPLEMENTING A STANDARDIZED SKIN INCISION, such a guide slot is used to create an incision of uniform length and depth for bleeding time applications.
The present invention belongs to the group of "slicing" lancet devices, and addresses the need for an even simpler, more painless incision method utilizing strictly linear blade motion.